Elsevier

Fluid Phase Equilibria

Volume 437, 15 April 2017, Pages 127-139
Fluid Phase Equilibria

Effect of composition and temperature variations on thermophysical properties of binary and ternary mixtures of 1-ethyl-3-methylimidazolium ethylsulfate with 1-butanol and/or methanol

https://doi.org/10.1016/j.fluid.2017.01.019Get rights and content

Highlights

  • ρ, u and η for [EMIM][ES] + 1-butanol or/and methanol have been measured.

  • The VE, κsE, Кs,mE and Δη have been calculated using experimental ρ, u and η data.

  • The parameters have been discussed in terms of intermolecular forces.

  • The excess/deviations properties have been fitted to Redlich-Kister equations.

Abstract

The thermophysical properties, densities, ρ, speeds of sound, u and dynamic viscosities, η of pure ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate, ([EMIM][ES]), and solvents 1-butanol, methanol and of their binary and ternary mixtures have been measured experimentally at a temperature range from (298.15–323.15) K, with an interval of 5 K and at pressure 0.1 MPa by using Anton Paar vibrating tube density and sound velocity meter DSA 5000M and Lovis microviscometer 2000M. The excess molar volumes, VE, isentropic compressibilities, κs, molar isentropic compressibilities, Кs,m, excess molar isentropic compressibility, Кs,mE, and viscosity deviations Δη have been calculated using the experimental ρ, u and η data at the same temperature range and pressure for [EMIM][ES] + 1-butanol/methanol binary systems and the VE, κs, excess isentropic compressibility, κsE and Δη for ternary [EMIM][ES] + 1-butanol + methanol system. The VE, κsE, Кs,mE and Δη data for the studied binary/ternary systems have been fitted to Redlich-Kister equation. The variations in VE,κsE, Кs,mE and Δη values with changes in composition and temperature have been discussed in terms of hydrogen bonding, ion–dipole interactions and structural effects on mixing of ILs and solvents.

Introduction

Ionic liquids (ILs) have attracted the attention of researchers during the last few years owing to their large variety of chemical and technological applications. The interest of a number of research groups has been focused on thermophysical properties of mixtures containing ionic liquids [1], [2], [3]. ILs are usually composed of organic cations and organic/inorganic anions [4], [5]. The most attractive features of ILs are their wide liquid range, negligible vapor pressure and high electrical conductivity, as well as the ability to tune their physicochemical properties by varying the ion structure; the latter has led to their being known as “designer” solvents [6], [7], [8], [9], [10]. The properties such as good thermal stability, high ionic conductivity, good solvation ability, and a wide electrochemical window, make ionic liquids potential novel materials for a wide range of uses, including uses as solvents or catalysts for reactions, lubricants, heat transfer fluids, electrolytes in batteries, capacitors, fuel, and solar cells and media for gas absorption and for liquid separation processes [11], [12], [13], [14], [15], [16]. Thermophysical properties are of utmost importance for the design of new ionic liquids to meet specific requirements. Since the variation of ion pairs gives rise to a great number of ionic liquids with a wide variety of properties, an understanding of solute-solvent interactions is helpful in designing the new IL [17], [18], [19]. In spite of the importance and applicability of ionic liquids and molecular solvents mixtures, the accurate and extensive studies of their fundamental physical and chemical properties are scarce. Studies on physical and chemical properties of ionic liquids, property measurement methodology, high-quality data on reference systems, standards for reporting thermodynamic data and the creation of a comprehensive database have been promoted by NIST [20], IUPAC [21] and DDB (the Dortmund Data Bank) [22]. The studies of thermodynamic and transport properties, like density, speed of sound and viscosity of IL + molecular solvent mixtures are interesting both from practical and theoretical point of view. Moreover, the knowledge of excess properties helps us to understand the structure-property relation, making it easier to search for an optimal ionic liquid for a specific application. One promising ionic liquid 1-ethyl-3-methyl-imidazolium ethylsulfate ([EMIM][ES]) is water-miscible, air-stable, and has a relatively low viscosity [23]. A number of authors have studied the thermophysical properties of pure 1-ethyl-3-methylimidazolium ethylsulfate and its binary and ternary mixtures with organic solvents at different temperatures and at atmospheric pressure [4], [6], [24], [25], [26], [27], [28], [29], [30]. There has not been found any study in literature on the thermophysical properties of binary and ternary mixtures of 1-ethyl-3-methylimidazolium ethyl sulfate with 1-butanol and/or methanol at T = (298.15–323.15) K and at pressure 0.1 MPa.

In this study, the thermophysical properties, densities, speeds of sound and dynamic viscosities of pure 1-ethyl-3-methylimidazolium ethylsulfate, ([EMIM][ES]), 1-butanol, methanol and of their binary mixtures [EMIM][ES] + 1-butanol, [EMIM][ES] + methanol and 1-butanol + methanol and of their ternary mixtures [EMIM][ES] + 1-butanol + methanol have been measured experimentally covering the entire range of composition at temperatures (298.15, 303.15, 308.15, 313.15, 318.15, 323.15) K with an interval of 5 K, and at pressure 0.1 MPa. The excess molar volume (VE), isentropic compressibilities (κs), molar isentropic compressibilities (Кs,m), excess isentropic compressibility (κsE), excess molar isentropic compressibility (Кs,mE), and viscosity deviation (Δη) values have been calculated using the experimental densities, speeds of sound and dynamic viscosities data of pure components and of their binary/ternary mixtures. The experimental VE, Кs,mE and Δη values of binary systems of [EMIM][ES] + 1-butanol, [EMIM][ES] + methanol and 1-butanol + methanol whereas VE, κsE and Δη values of ternary system of [EMIM][ES] + 1-butanol + methanol have been correlated to Redlich-Kister equation [16], [31]. The behavior of excess and deviations properties have been discussed in terms of ion-ion, ion-dipole, dipole-dipole and hydrogen bonding interactions and packing of components in the studied mixtures [24].

Section snippets

Materials

The source, purification method, mass fraction purity and water content of 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][ES], 1-butanol and methanol were used in this work are listed in Table 1.

Apparatus and procedure

Water content of pure [EMIM][ES] was measured by Karl Fischer coulometric titrator (C20, Metller Toledo), and was found to be 192 ppm. The binary mixtures, [EMIM][ES] + 1-butanol, [EMIM][ES] + methanol and 1-butanol + methanol and ternary mixture, [EMIM][ES] + 1-butanol + methanol of different mole

Density, speed of sound and viscosity

The measured densities, speeds of sound and viscosities of pure [EMIM][ES], 1-butanol and methanol and of their binary mixtures at the temperatures (298.15, 303.15, 308.15, 313.15, 318.15, and 323.15) K and at 0.1 MPa pressure have been reported in Table 2, Table 3, Table 4, Table 5, respectively. The measured values of densities, speeds of sound and viscosities of pure [EMIM][ES] [6], [24], [25], [26], [27], [28], [29], 1-butanol [32], [33], [34] and methanol [35], [36], [37], [38], [39], [40]

Conclusion

The excess molar volume values have been found to be negative at all composition and temperature and decrease with an increase in temperature for each binary system [EMIM][ES] + 1-butanol, [EMIM][ES] + methanol and 1-butanol + methanol. Similarly, the Кs,mE values have also been found to be negative at all composition and temperature and decrease with an increase in temperature. The Δη values are found to be negative at all composition and temperature and increase with an increase in

Acknowledgements

The authors are thankful to the Chairman Department of Chemistry, A.M.U., Aligarh for providing the necessary facility for the compilation of this work. Financial support from the UGC (Major Research Project) F. No. 41-240/2012(SR) scheme is acknowledged.

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